S27E42: Martian Oasis: Gale Crater's Watery Past Revealed

[00:00:00] This is SpaceTime Series 27 Episode 42 for broadcast on the 5th of April 2024.

[00:00:06] Coming up on SpaceTime claims that what a persistent Mars' girl creator for longer than previously thought,

[00:00:13] the Sun's spectacular double solar flare.

[00:00:16] And persistent reports that the Pentagon really is testing a successor to the SR-71 Blackbird.

[00:00:23] All that and more coming up on SpaceTime.

[00:00:30] With Stuart Gary

[00:00:47] Scientists have found signs that what was abundant in Mars' girl creator,

[00:00:51] long after the red planet was thought to become dry and inhospitable.

[00:00:56] The findings reported in the journal Geology have implications for scientists understanding

[00:01:01] of the changing climate on Mars as well as where scientists should be looking for signs of habitability.

[00:01:07] Billions of years ago Mars was home to abundant water and its girl creator contained a large lake.

[00:01:14] Gradually however, the climate changed, turning the once warm wet world into a dusty,

[00:01:20] freeze-dried desert. Using data and images from NASA's Mars Curiosity rover,

[00:01:25] the authors found clues of deformed layers within a desert sandstone that they argue could have only

[00:01:31] been formed by water. Now while they agree that water was present early on, they're uncertain as

[00:01:37] to whether it existed as a pressurized liquid, an ice or a salty brine. The studies lead

[00:01:43] author Stephen Bannum from Imperial College London says the sandstone revealed that the

[00:01:48] water was probably abundant more recently and for longer than previously thought.

[00:01:53] He says it might have been a pressurized liquid forced into and deforming the sediment,

[00:01:57] frozen with a repeated freezing and thawing process causing deformation, or briny and subjected to

[00:02:04] large temperature swings. What is clear is that behind each of these potential ways to

[00:02:09] deform the sandstone, water was the common link. Scientists accept that most water on the red

[00:02:14] planet was lost by the middle of the Spirian period which lasted from 3.7 to 3 billion years

[00:02:20] ago. These new findings suggest that water was in fact still abundant underground near the surface

[00:02:26] of Mars towards the latter Spirian. To better understand the planet's past climate suitability

[00:02:31] for life, researchers are using the Curiosity rover to look for clues in the Mars rock record.

[00:02:37] The six-wheeled car-sized mobile laboratory has been exploring the 154-kilometre wide

[00:02:43] gale crater basin just south of the equator as well as the northern flank of its central

[00:02:47] mountain called Mount Sharp since 2012. The 5.5-kilometre high Mount Sharp was built up in layers,

[00:02:55] first by incoming lake and river sediments and later by desert sediments and winds during Mars'

[00:03:01] supposed period of drying. Using Curiosity's main scientific instrument, Mascam, researchers

[00:03:07] collected images of Mount Sharp sedimentary layers to find the fingerprints of how the

[00:03:12] rocks were formed. They were looking at rocks that were deposited in what is now a sandy

[00:03:16] desert and found structures within that indicated water. Vanim says that when sediments are moved by

[00:03:23] flowing water in rivers or by the wind blowing, they leave characteristic structures which can

[00:03:28] act like fingerprints of the ancient processes that formed them. As Curiosity's continued to

[00:03:33] ascend Mount Sharp, it's encountered increasingly younger rocks deposited in progressively drier

[00:03:39] environments. It eventually reached a sandstone deposit draped over the mountainside known as

[00:03:44] the Stimson Formation, the preserved relic of a desert containing large sand dunes. The images

[00:03:50] it collected revealed that the formation was deposited after Mount Sharp had formed during

[00:03:55] Mars' period of supposed drying. They also revealed that part of the formation contained

[00:04:01] features that had clearly been influenced by water. Usually the wind deposit sediments are

[00:04:06] very regular and predictable ways. But surprisingly these wind deposited layers were

[00:04:12] torded into strange shapes which suggested that the sand had been deformed shortly after it was

[00:04:17] laid down. It's these structures which point to the presence of water just below the surface.

[00:04:23] Generally speaking, the layers of sediment in the crater reveal a shift from a wet environment

[00:04:27] to a dry one over time, reflecting the transition of the red planet from a humid and habitable

[00:04:33] environment to an inhospitable desert world. But these water form structures in the desert

[00:04:39] sandstone show that water did persist on the red planet much later than previously thought.

[00:04:44] The researchers' discoveries' implications for future space exploration missions,

[00:04:49] especially those searching for life beyond Earth. On Mars, the Stimson Formation and similar

[00:04:54] desert sandstones were previously considered less promising targets when hunting for biosignatures

[00:05:00] evidence of past primordial life. Needless to say, finding these water form structures

[00:05:06] changes that notion. This is space time. Still to come, the sun erupts with a spectacular double

[00:05:13] solar flare and could the aurora be real after all? Persistent reports that the Pentagon is

[00:05:19] testing a successor to the SR-71 Blackbird. All that and more still to come on space time.

[00:05:36] The sun has become increasingly active over the past week with an almost continuous display of

[00:05:47] solar flare activity, including a spectacular double solar flare event described as the most

[00:05:52] powerful eruption since 2017. The growing spate of solar flares spewing into space suggests

[00:05:58] the sun is getting very close to solar maxima, the climax of its 11 year solar cycle.

[00:06:04] After a month of relatively low level activity, the sun has now produced a powerful X1.1 class solar

[00:06:10] flare followed by almost a dozen smaller M class solar flares and a bright coronal mass ejection

[00:06:17] triggering spectacular auroral activity at higher latitudes here on Earth. Solar flares

[00:06:23] are an eruption of electromagnetic radiation in the sun's atmosphere caused by the snapping

[00:06:27] of twisted magnetic field lines above sunspots. Sunspots are cooler darker regions to the sun's

[00:06:34] surface that form when magnetic field lines rise from deep below the sun's visible surface.

[00:06:40] The spectacular X1.1 solar flare resulted from two sunspots and was directly targeted towards

[00:06:46] the Earth. Solar flares are classified by severity with B class being the weakest

[00:06:51] followed by C, M and X being the strongest and most powerful. The jump from one letter to the next

[00:06:58] constitutes a 10 fold increase in energy output much like the Richter scale for earthquakes

[00:07:03] and the enhanced Vegeta scale for tornadoes. When a big solar flare occurs it's often followed

[00:07:09] by coronal mass ejection, a massive release of plasma and magnetic field from the sun's

[00:07:14] outer atmosphere. Now if one of these solar mass ejections happens to be pointing towards

[00:07:19] the Earth they'll trigger powerful geomagnetic storms as the charged particles from the sun

[00:07:24] slam into Earth's magnetic field causing the whole magnetosphere to literally wobble like

[00:07:29] jello. The ionised particles then travel along Earth's magnetic field lines towards the North

[00:07:34] and South poles in the process triggering the Northern and Southern lights the Aurora

[00:07:39] Borealis and Aurora Australis. But they can also take out satellites short circling equipment

[00:07:45] they can cause communications and navigation system blackouts, increase radiation doses to

[00:07:51] astronauts in space and affect power grids and communication systems on the ground.

[00:07:56] For this event for the first time the European Space Agency's unlikely space where the duo

[00:08:01] Smars and the Swarm were able to track the severe solar storm as it warped Earth's magnetic field.

[00:08:07] For Swarm scientists monitoring the Earth's magnetic field it was the perfect opportunity

[00:08:12] to put the three satellite constellations new near Earth real-time data to good use.

[00:08:17] Each Swarm satellite carries a magnetometer to measure the strength of Earth's magnetic field.

[00:08:22] The magnetic field around the Earth is constantly changing and it responds especially strongly to

[00:08:27] space weather events. And the coronal mass ejection triggered by the double solar flare event

[00:08:32] arrived much sooner than expected causing a powerful geomagnetic storm reaching severe

[00:08:37] levels. As the data quickly became available Swarm Alpha was the first of the low Earth orbiting

[00:08:43] satellites to measure changes in Earth's magnetic field and Swarm Bravo soon provided another

[00:08:49] perspective showing large changes to Earth's magnetic field reaching lower lightitudes during

[00:08:54] its peak. While the solar storm itself was relatively short lived the disturbance to

[00:08:58] Earth's magnetic field was incredibly strong and the impacts are still being analyzed.

[00:09:04] According to the European Space Agency Space Weather Office the active region of the Sun

[00:09:08] responsible has been releasing further M-class solar flares though not quite as strong.

[00:09:14] And there's still a 40% chance of further X-class flares in coming days before this

[00:09:19] active region of the Sun rotates to the Sun's opposite side away from Earth.

[00:09:24] Now somewhat surprisingly ESA's Soil Moisture and Ocean Solidity Satellite SMOS was among

[00:09:29] the first in line to capture the solar radio burst associated with the flare. See the main

[00:09:35] instrument on SMOS is an interferometer radiometer which normally detects L-band radio waves emitted

[00:09:41] from Earth. This allows scientists to measure geophysical parameters like soil moisture,

[00:09:46] sea surface salinity and sea ice thickness. This report from ACETV.

[00:09:52] On November the 2nd 2009 SMOS was launched from the Plissets Cosmodrome on top of a

[00:09:58] rocket launcher. SMOS is one of ESA's Earth Explorer missions that address key scientific

[00:10:04] challenges and demonstrate new technology in space. Carrying a novel instrument to return

[00:10:10] information on soil moisture and ocean salinity both key components of the Earth's water cycle.

[00:10:17] SMOS is advancing our knowledge of how water is cycled between the Earth's surface

[00:10:22] and the atmosphere. Understanding these exchange processes is crucial for understanding climate

[00:10:28] change, for improving weather prediction and for example helping to optimize water consumption

[00:10:34] when growing crops. SMOS measures directly the surface soil moisture so this is really the

[00:10:41] kind of rain gauge of the atmosphere so we collect the rain and we store it. Measuring

[00:10:47] surface soil moisture gives us a hint on the rainfall so we can partition the rainfall but

[00:10:52] also looking at its evolution we can link it to different other things. One of them is of course

[00:10:58] dryness or wetness of the soil so floods or droughts but also the fact that the impact of

[00:11:06] other events such as El Nino or La Nina and its impact on the rainfall distribution

[00:11:12] hence the wetness so it is used to infer or droughts or monitor the droughts but also of

[00:11:20] course for food security in many regions to anticipate crop yield especially in areas which are

[00:11:27] limited by rainfall. This research satellite was originally planned to be in orbit for five years

[00:11:33] but thanks to Europe's technological excellence it has already doubled its life in orbit

[00:11:39] providing time series data for a variety of applications. For instance SMOS data is used for

[00:11:46] ESA's climate change initiative through which data are compiled to understand how climate

[00:11:52] variables are changing over time. Its data are also combined with data from other satellites

[00:11:58] such as Cryosat to map the thickness of sea ice a crucial climate variable. With SMOS we have

[00:12:05] the possibility to measure the sea ice thickness in particular the thickness of thin ice we can

[00:12:13] measure with SMOS. We have also the companion the ESA Earth Explorer Cryosat this was specifically

[00:12:23] designed to measure the sea ice thickness and Cryosat is great to measure the thickness of

[00:12:28] thick ice from the freeboard but with SMOS we can accurately measure the thin ice.

[00:12:35] SMOS data are also used to map the freezing and thawing of soil this is important because frozen

[00:12:42] soil and in particular permafrost acts as a carbon sink when permafrost thaws carbon is

[00:12:49] released back into the atmosphere amplifying the greenhouse effect by comparing data over

[00:12:55] several years. SMOS helps us to better understand variables affected by and affecting climate change.

[00:13:02] Over the years SMOS has proven to be a versatile satellite going way beyond its original scientific

[00:13:08] goals. Today SMOS data are even used operationally for weather prediction by organizations such as

[00:13:16] the European Center for Medium Range Weather Forecasts. SMOS is very important for

[00:13:23] weather prediction because weather is related to forecasts of the atmospheric variables but it's

[00:13:31] also related to land surface forecast and ocean forecast river forecast and for this for weather

[00:13:38] prediction our strategy is to develop an earth system approach where we have a consistent

[00:13:44] forecast for the different components of the earth system and in this context variables which are at

[00:13:53] the interface between land surface and atmosphere or ocean and atmosphere are very important to

[00:14:00] ensure the consistency across the different earth system components and supposed exactly that

[00:14:05] it is providing information at the interface between the different earth system component.

[00:14:10] SMOS has given the scientific community an unprecedented wealth of data and while it has

[00:14:16] long surpassed its intended lifespan SMOS remains hard at work while new missions are being studied

[00:14:21] and prepared to ensure continuous datasets with even higher resolutions and improved technology.

[00:14:28] Now due to its position in orbit however SMOS's antenna also has the sun in its field of view

[00:14:34] and solar flares also release radio waves. Now for earth observation these signals are removed as noise

[00:14:41] but space where the scientists had other ideas with almost 24 hours of near real-time monitoring

[00:14:47] of the sun SMOS can detect the effects of solar flares on global navigation satellite systems

[00:14:52] as well as flight radar and L-Bank communications having this near real-time information is

[00:14:58] incredibly useful for example following an especially strong solar flare in December last year

[00:15:04] a number of satellites lost their GPS contact with ground stations in South America.

[00:15:09] SMOS was able to narrow down the cause linking it to the solar event this is space time

[00:15:16] still to come is Aurora real after all assistant reports that the Pentagon is testing a successor

[00:15:23] to the SR-71 Blackbird and our nearest neighboring star system Alpha Centauri the iconic constellation

[00:15:31] Southern Cross and the annual Lyraids meteor shower are among the highlights of the April

[00:15:36] night skies on Skywatch.

[00:15:54] There are persistent reports coming out of Washington that the Pentagon has developed

[00:15:58] and is now testing a successor to the famous A-12 SR-71 Blackbird the world's fastest jet.

[00:16:05] The unconfirmed reports suggest Lockheed Martin's scunt works in California are working on a new

[00:16:10] unmanned hypersonic aircraft so-called SR-72 son of Blackbird which will be ready to take to the

[00:16:17] skies next year. The secret hypersonic aircraft is said to be capable of Mach 6 that's over

[00:16:23] 6,400 kilometers per hour and that would make it the fastest plane ever developed.

[00:16:30] Its primary functions will likely be intelligence surveillance and reconnaissance

[00:16:34] gathering activities similar to those undertaken by its predecessor the Blackbird.

[00:16:39] The aircraft's combat systems are said to be able to launch hypersonic weapons faster than any other

[00:16:44] weapons carrying platform meaning they can instantly achieve hypersonic speeds.

[00:16:49] Like its SR-71 predecessor the SR-72 whether it's called Dark Star Aurora or whatever will

[00:16:55] be about 30 meters long incredibly stealthy in shape and flight altitudes of around 90,000 feet

[00:17:02] or more. Power will come from fully reusable turbine-based combined cycle hypersonic engines

[00:17:08] which combine turbofan engines used for takeoff and landing with a supersonic combustion ramjet

[00:17:13] or scramjet capable of achieving and sustaining speeds above Mach 5. The SR-71 was originally

[00:17:20] developed as the Black project from Lockheed Martin's A-12 reconnaissance aircraft during

[00:17:25] the 1960s by the company's Harley-Segretive Skunk Works. The original A-12 could reach

[00:17:31] altitudes of over 80,000 feet or 24 kilometers and at a top speed of over Mach 3.1. The SR-71

[00:17:39] derivative could reach over 90,000 feet and a speed of Mach 3.2. It was slightly longer and heavier

[00:17:45] than the A-12 allowing it to hold more fuel as well as a two seat cockpit. Now as far as we

[00:17:51] can tell 12 A-12s were built for the CIA followed by two M21 drone carriers three YF-12 high

[00:17:58] altitude interceptor prototypes for the US Air Force and then 32 SR-71 strategic reconnaissance

[00:18:05] aircraft. The spy planes kept flying until the late 1990s with the last being used for

[00:18:11] scientific research by NASA. They currently hold every aviation speed and altitude record

[00:18:17] for an air breathing jet aircraft. This is spacetime.

[00:18:38] And time out to check out the night skies of April on Skywatch. April is the fourth month of the

[00:18:43] year in the Gugorean calendar and the fifth in the early Julian calendar. The Romans gave this month

[00:18:49] the Latin name of Prylus. Although the names origins aren't certain, traditional entomology

[00:18:55] suggests it's from the verb apyriar to open as in it being the season when the trees and

[00:19:00] flowers begin to open as the northern hemisphere moves into spring. April is also a prevention

[00:19:06] of cruelty to animals month and so it's a good time to consider adopting a shelter pet

[00:19:11] or donating to an animal welfare charity. High in the southern sky during April you'll find the

[00:19:18] Southern Cross and it's two pointer stars Alpha and Beta Centauri. The more distant of the two

[00:19:24] pointer stars from the Southern Cross is Alpha Centauri which also happens to be the nearest

[00:19:29] star system to our own. Located some 4.3 light years away Alpha Centauri actually consists of

[00:19:35] three stars. There's Alpha Centauri A and B which orbit each other and Proxima Centauri which orbits

[00:19:42] the pair and at 4.25 light years distant is currently the nearest star to the earth other than the sun.

[00:19:49] A light year is about 10 trillion kilometers. The distance of photon can travel in a year

[00:19:54] at 300,000 kilometers per second, the speed of light in a vacuum and the ultimate speed limit

[00:20:00] of the universe. Like the Sun Alpha Centauri A is a Spectral type G yellow dwarf star. It's slightly

[00:20:08] bigger having about a tenth more mass than the Sun and it's about 50% more luminosity.

[00:20:14] Astronomers describe stars in terms of spectral types, a classification system based on temperature

[00:20:20] and characteristics. The hottest most massive and most luminous stars are known as Spectral

[00:20:26] type O blue stars. They're followed by Spectral type B blue white stars then Spectral type A white

[00:20:33] stars, Spectral type F whitish yellow stars, Spectral type G yellow stars that's where our sun

[00:20:39] fits in, Spectral type K orange stars and the coolest and least massive stars of all are

[00:20:45] Spectral type M red dwarf stars. Each spectral classification is further subdivided using a

[00:20:51] numeric digit to represent temperature with zero being the hottest and nine the coolest

[00:20:57] and then a Roman numeral to represent luminosity. So our sun is a Spectral type G2v or G25

[00:21:06] yellow dwarf star. Also included in this stellar classification system are Spectral types LT and

[00:21:12] Y which are assigned to failed stars called brown dwarves. These are sometimes born as

[00:21:18] Spectral type M red dwarf stars that become brown dwarves after losing some of their mass.

[00:21:24] Brown dwarves fit into a category between the largest planets which are about 13 times the

[00:21:29] mass of Jupiter and the smallest Spectral type M red dwarf stars which are around 75 to 80 times

[00:21:35] the mass of Jupiter or about 0.08 solar masses. Opening in a binary system with Alpha Centauri

[00:21:43] A is Alpha Centauri B a Spectral type K orange dwarf star a little smaller and cooler than the

[00:21:50] sun with about 0.9 times the sun's mass and about half its luminosity. Alpha Centauri A and B

[00:21:57] orbit each other around a common center of gravity every 79.91 Earth years. The distance

[00:22:04] between the two stars varies between roughly that of Pluto in the sun and that of Saturn in

[00:22:09] the sun. The third star in the system Proxima Centauri sometimes called Alpha Centauri C is a

[00:22:15] Spectral type M red dwarf star with roughly a seventh the diameter and about an eighth the mass of the

[00:22:20] Sun. It takes around 550,000 Earth years to orbit Alpha Centauri A and B. The nearer of the two

[00:22:29] pointer stars to the Southern Cross is Beta Centauri also a triple star system but this one

[00:22:34] located a far more distant 390 light years away. All three are massive young blue stars far larger

[00:22:42] and more luminous than the Sun. Two of the stars named Beta Centauri A and A and Beta Centauri A

[00:22:48] B orbit each other while the third star Beta Centauri B orbits the primary pair every 1500

[00:22:55] Earth years. Beta Centauri A, A and A B are known as a spectroscopic binary orbiting

[00:23:01] each other every 357 Earth days. Spectroscopic binaries are double star systems orbiting each

[00:23:07] other so closely and at such an angle that they can only be visually separated from our point of

[00:23:12] view here on Earth at least by their spectroscopic signatures. Both these stars are now reaching

[00:23:18] the end of their time on the main sequence and will soon run out of the core hydrogen they

[00:23:23] use for fusion, the process which makes stars like the sunshine. The two pointer stars Alpha

[00:23:29] and Beta Centauri are named after Sauron the Centaur a mythological Greek being Half Man, Half Horse.

[00:23:36] Sauron taught many of the Greek gods and heroes but was placed among the stars after accidentally

[00:23:41] being shot with a poison arrow by Hercules. Next to the pointer stars is the spectacular

[00:23:48] Southern Cross or crux the smallest but one of the best known of the 88 constellations in the

[00:23:54] sky. The Southern Cross is considered an important constellation for navigation and is featured

[00:23:59] on the flags of several nations including Australia, Brazil, New Zealand, Papua New Guinea and Samoa.

[00:24:06] In April the Southern Cross lies on its side in the early evening but becomes more and more

[00:24:11] upright as the night progresses. The bottom and brightest star in the Southern Cross is Alpha

[00:24:18] Cruces or A Crocs which is actually a multiple star system located 321 light years away.

[00:24:24] It consists of three stars A1 Cruces which is a spectroscopic binary and A2 Cruces.

[00:24:31] A2 Cruces in the primary star in A1 Cruces are both spectral type B blue stars with surface

[00:24:38] temperatures of 26,000 and 28,000 Kelvin respectively. The two components orbit each other every

[00:24:45] 1500 Earth years at an average distance of around 430 astronomical units. An astronomical unit is

[00:24:52] the average distance between the Earth and the Sun roughly 150 million kilometers or 8.3 light

[00:24:58] minutes. The spectroscopic binary A1 Cruces is thought to comprise two stars with about 10

[00:25:06] and 14 times the mass of the Sun respectively. The pair orbit each other every 76 Earth days

[00:25:12] at a distance of around 150 million kilometers in other words one astronomical unit. The masses

[00:25:18] of A2 Cruces and the larger component of A1 Cruces are expected to eventually explode as

[00:25:24] core collapse supernovae ending up as neutron stars while the smaller component of A1 Cruces

[00:25:30] could survive as a white dwarf. The left hand and second brightest star in the Southern Cross

[00:25:36] is called Beta Cruces and it's also a spectroscopic binary consisting of two stars

[00:25:41] orbiting each other every five Earth years at an average distance which varies between 5.4 and 12

[00:25:47] astronomical units. Beta Cruces is located some 280 light years away. The primary star Beta Cruces A

[00:25:55] is a spectral type B Beta Cephe variable blue star which changes in brightness over a period

[00:26:01] of around 4 to 4 and a half hours. It has about 16 times the Sun's mass, about 8 times its

[00:26:07] diameter and a surface temperature of some 27,000 Kelvin. By comparison our Sun is the surface

[00:26:14] temperature of just 6,000. The second star in the system Beta Cruces B has about 10 solar masses.

[00:26:21] A third companion has also been detected in the system however it appears to be a low mass

[00:26:26] pre-main sequence star which hasn't yet commenced nuclear fusion. Nebeta Cruces

[00:26:32] is the spectacular young open star cluster known as the Capacruces cluster or NGC 4755

[00:26:40] and more commonly referred to as the dual box. The name given to it by famous 18th century

[00:26:46] astronomer John Herschel. Open star clusters are groups of stars which were originally

[00:26:51] all born at the same time out of the same collapsing molecular gas and dust cloud.

[00:26:57] Although somewhat still gravitationally bound to each other, stars in open clusters eventually

[00:27:02] separate moving to other parts of the galaxy. As the name suggests, the dual box is a stunning

[00:27:08] collection of more than 100 bright colourful stars located some 6,440 light years away

[00:27:15] although its exact distance is somewhat difficult to determine because of the nearby Colesack Nebula

[00:27:20] which obscures some of the light. The Colesack is a dark nebula containing lots of gas and

[00:27:25] dust blocking out background stars. In Australian Aboriginal Dream Time legend,

[00:27:31] the Colesack forms the head of the emu constellation with the dark dust lanes of the Milky Way

[00:27:36] forming the emus body and legs. The central parts of the dual box are framed by bright stars making

[00:27:43] up an A shaped asterism. These are among the brightest known blue, white and red supergiants

[00:27:50] in the Milky Way. Gamma Cruces which is located at the top of the Southern Cross

[00:27:55] is the third brightest star in the constellation. It's also one of the nearest red giants to

[00:28:00] our solar system located just 88.6 light years away. Although only 30% more massive than the Sun,

[00:28:07] its expanded outer envelope is bloated after some 84 times the Sun's radius and is radiating some

[00:28:14] 1500 times more luminosity than the Sun. As a red giant no longer on the main sequence,

[00:28:20] Gamma Cruces is nearing the end of its life. Its surface temperature is some 3626 Kelvin

[00:28:28] and it has a prominent reddish-orange appearance. The star on the right hand side of the Southern

[00:28:34] Cross is Delta Cruces, a massive hot and rapidly rotating star that's in the process of evolving

[00:28:40] into a red giant and will eventually end up as a white dwarf, the stellar corpse of sun-like stars.

[00:28:46] Delta Cruces is located some 345 light years away and is about 9 times the Sun's mass

[00:28:53] and 8 times its radius. It's presently radiating at around 10,000 times the luminosity of the Sun

[00:28:59] at an effective temperature of 22,570 Kelvin causing it to glow with a blue-white hue.

[00:29:06] The smallest star in the Southern Cross is Epsilon Cruces which is located in the space

[00:29:10] between Delta and Alpha Cruces. It's a red giant some 228 light years away. It is about

[00:29:18] 1.42 times the mass of the Sun and about 32 times its radius. Its surface temperature of 4148 Kelvin

[00:29:27] means it's sometimes referred to as an orange giant. The Southern Cross is at its highest point

[00:29:33] in the southern sky this time of year and is pointing directly at the southern celestial pole.

[00:29:38] It's within the constellation Centaurus the Centaur, the half-man, half-horse of Greek

[00:29:43] mythology we mentioned earlier. The creature is holding a bow loaded with an arrow. The Centaur's

[00:29:50] front leg is marked by the two pointer stars Alpha and Beta Centaurus. His back arches over the

[00:29:56] Southern Cross and just above this is Omega Centauri, a spectacular globular cluster visible with

[00:30:02] the unaided eye from dark locations. Unlike open star clusters, globular clusters are

[00:30:09] tightly packed spheres containing thousands to millions of stars which were originally all

[00:30:14] thought to have been born at the same time from the same molecular gas and dust cloud.

[00:30:19] Omega Centauri is about 16,000 light years away. It's one of the largest and brightest of

[00:30:26] the hundreds of globular clusters known to orbit around the Milky Way Galaxy.

[00:30:30] Centaurus was included among the 48 constellations listed by the second century astronomy

[00:30:36] and it remains one of the 88 modern day constellations. The constellation Orion the

[00:30:42] Hunter is still clearly visible in the northwestern sky this time of year with its rectangle of four

[00:30:48] stars surrounded by a central trio of stars which form Orion's belt. To the right or east of

[00:30:55] Orion is the constellation Gemini and its two brightest stars Paulax and Caster. This

[00:31:01] time of year the Gemini twins are almost directly due north for southern hemisphere

[00:31:05] sky watches. The higher of the two stars Paulax is a red giant some 11 times the diameter of the

[00:31:12] sun and located just 34 light years away. The other star Caster is much further away

[00:31:18] some 51 light years. Look to the east and you'll see the star Regulus the brightest star in

[00:31:24] the constellation of Leo the Lion. Regulus which means little king is located 77 light

[00:31:30] years away and it's about three and a half times as massive as the sun at about 140 times as luminous.

[00:31:37] Regulus is a binary companion star which takes 130,000 years to orbit the primary.

[00:31:43] To the right of Regulus and virtually due east in the sky right now is the star Spiker.

[00:31:50] Located directly below the four stars in the constellation Corvus the Crow

[00:31:54] Spiker is the brightest star in the constellation Virgo also known as Alpha Virginus it's the 16th

[00:32:00] brightest star in the night sky and is another spectroscopic binary comprising two stars closely

[00:32:07] orbiting each other every four Earth days. In fact the two stars in Spiker orbiting so close

[00:32:13] together that the gravitational interaction between them has caused them to become

[00:32:17] rotating epsoleutal variables distorting them into the shape of a rugby league or

[00:32:22] gridiron football. Light from this binary changes in brightness as the two stars orbit each other

[00:32:28] exposing their elongated hemispheres to us. Spiker is located some 260 light years away

[00:32:34] and is some 2000 times as luminous as the sun. Spiker means air of wheat which Virgo is holding

[00:32:42] in a hand it's so named because it marks the start of the harvest season in the northern

[00:32:47] hemisphere. The primary is the blue giant variable Beta Sepheid which undergoes small rapid variations

[00:32:54] in brightness because of pulsations in the star surface thought to be caused by the unusual properties

[00:33:00] of iron at temperatures of 200 000 degrees in the stellar interior. It is about 10 times the sun's

[00:33:06] mass and about seven and a half times its diameter. Once a spectrotype B blue white main

[00:33:12] sequence star it's now pulsating rapidly rotating at more than 199 kilometers per second over a 0.1738

[00:33:20] Earth Day period. It's one of the nearest stars to the earth which is expected to end its life

[00:33:26] as a type 2 core collapse supernova. The second star in the system is also thought to be a

[00:33:32] spectral type B blue white giant about seven solar masses and 3.6 times the sun's diameter.

[00:33:39] Okay going back to the southern cross and looking to the right or west you'll see the

[00:33:43] star Canopus. It's the second brightest star in the night sky after Sirius. Even though Canopus is

[00:33:50] 312 light years away it looks incredibly bright because it's huge 100 times the diameter of

[00:33:56] the sun and 10 000 times as luminous. This year's second major meteor shower the Lyrids

[00:34:02] will peak on April the 22nd and 23rd. The Lyrids appear to radiate out from the constellation Lyra

[00:34:09] close to the star Vega one of the brightest stars in the sky this time of year. The source of the

[00:34:14] meteor shower are particles of dust and debris shed by the long period comet C1861 G1 Thatcher.

[00:34:22] Sky watches in the northern hemisphere get the best view of the Lyrids. However listeners at

[00:34:27] mid southern hemisphere attitudes can also see the shower between midnight and dawn.

[00:34:32] Patient observers will be rewarded with around 18 meteors per hour before dawn from dark sky locations.

[00:34:39] And now with a look at what else is happening in the Apple night skies we're joined by Jonathan

[00:34:43] Nally from Sky and Telescope magazine. Hello Sirius well it's the middle of autumn here in

[00:34:48] the southern hemisphere so we're starting to get to the winter constellations now they're

[00:34:51] starting to make an appearance. So as night falls we can see the Milky Way stretching across

[00:34:56] the sky from the southeast to the northwest during the first half of the night by the early

[00:35:00] morning hours that the earth hadn't turned a bit more on a axis. The Milky Way will now stretch

[00:35:04] from the southwest to the northeast and how much you see of the Milky Way by the way will depend

[00:35:09] on how dark your local skies are you know the area around where you live and the darkest

[00:35:13] of your skies have to say depends on how much or how little light pollution there is which

[00:35:18] is street lights sporting field lights house lights advertising and shop lighting and so

[00:35:23] on it's a real problem for most people because most people live in cities and you know all this

[00:35:27] waste of light that's you know most light that is out there from these artificial lights at night

[00:35:31] time most of the light just goes anywhere except where it's meant to go it's usually

[00:35:34] just meant to illuminate the ground but you know it's going sideways and upwards and all over

[00:35:38] the place just crazy because it's not only ruins the night sky but it's just a lot of wasted

[00:35:42] energy too there's just what's the point of light shining sideways it's just all lights

[00:35:46] street lights should have hoods over them that direct the light downwards rather than

[00:35:50] shining out the side and up into space you know the very old style sorry I'm going around here

[00:35:54] the very old style um traditional long thin fluorescent street lights I seem to recall

[00:36:00] data from years ago showing that 80 percent of the light coming out of those things

[00:36:04] didn't go on the ground it just went in every other direction I think all the coal and stuff

[00:36:08] has been burned it could use 80 percent of light going somewhere where it's

[00:36:11] supposed to be that's why you can see these you know these pictures of the earth at night

[00:36:14] time you see all the city lights and everything what's the point of all that light shining up

[00:36:18] with certain total lights from here it's just it's just wrong it's just totally wasted light

[00:36:22] totally wasted energy anyway that's my rant that's what ruins seeing nookie way in the city because

[00:36:27] there's so much light pollution around that the faintest stuff up in the sky and the nookie way

[00:36:30] is safe it just gets drowned out anyway as the night rolls on the earth keeps turning a lot of

[00:36:35] the famous constellations that we've had around the last few months are going to start to drop

[00:36:38] out of here in the west such as taurus and orion others such as gemini and leo can still be

[00:36:44] seen in the northern part of the sky is seen in the mid southern latitudes or in the southern part

[00:36:49] of the sky between the northern hemisphere deep down south in the early evening the southern cross

[00:36:54] is nice and high it's up really nice and high we've got the bright star canopus the second

[00:36:58] brightest star in the sky it's up even higher in the south southwest and the brightest star in

[00:37:02] the sky serious is very very high in fact from where I live it's almost overhead this time of

[00:37:07] year in the sort of early to mid-event and it's because it's the brightest star in the sky

[00:37:10] well if you just tap this I mentioned canopus canopus is the star of the bright star in the

[00:37:16] constellation carina if you use a star map or not one of those mobile phone apps it shows you

[00:37:20] what's up in the night sky to identify carina then grab yourself a pair of binoculars if you've

[00:37:24] got them and just start sweeping through the star fields of carina the star clusters and

[00:37:30] nebulae and all this sort of thing and even if you are in light polluted sky you're still

[00:37:33] going to see quite a lot binoculars of what you need for this area it's just it's just

[00:37:37] really amazing and beautiful once you get the view of the night sky through binoculars or a small

[00:37:41] telescope you think wow yeah because look the stuff you just can't see with the naked eye it's too

[00:37:46] thin for your eyes to pick up at night time but just if a little bit of optical aid a bit of

[00:37:51] extra magnification and the extra light gathering power having larger lenses than your eyes are

[00:37:57] it pulls in more light and it's magnified and you start to see all this amazing stuff up there

[00:38:02] so give that a try if you've got a pair of binoculars or you know someone who has

[00:38:04] to the left of carina if you're looking south we've got the southern cross and right next door to it

[00:38:09] is a big dark nebulae called the coal sack and then very close to that are two stars known as

[00:38:15] pointers i call them the two pointers and they're alpha and beta centauri and it's interesting

[00:38:20] when you look at some of these stars because their brightness can't be used as a way to judge

[00:38:24] their distance from us because a nearby dim star might seem brighter than a more luminous star

[00:38:30] that's much further away so for instance you've got serious the star that seems to be the brightest

[00:38:35] which only 8.6 light years away but canopus is 310 light years away but it appears not that much

[00:38:41] dimmer than serious really that's because intrinsically canopus is a bigger hotter brighter

[00:38:46] star than serious it's just that it's 310 light years away and series is 8.6 so series is a smaller

[00:38:53] dimmer star than canopus but it's so much closer and that's why it appears brighter so when

[00:38:57] you see stars when you look up and see stars you think oh that star's really bright it must be close

[00:39:01] to us that's not necessary to the case now some of the dimmer stars out there maybe dozens of times

[00:39:06] brighter than the brightest star you can see is just near a lot further away and this is all

[00:39:10] different from magnitude when astronomers are looking at the the brightness is something in

[00:39:14] the sky well yeah magnitude is as a measure of brightness um so we said that star's a magnitude

[00:39:20] one star uh a magnitude two star is dimmer than a magnitude one a magnitude three star is dimmer

[00:39:26] than a magnitude two a magnitude zero star is brighter than the magnitude one star and the

[00:39:32] magnitude minus one is brighter than a magnitude zero star serious i think is minus 1.5 1.6 something

[00:39:41] like that so it's the brightest in what they call apparent magnitude now there are two different

[00:39:45] magnitude measurements one is apparent magnitude that's how bright something appears to us when

[00:39:50] we look at it just up there in the night sky right not taking into account its distance

[00:39:54] from us it's just how bright it appears to us so serious is to be very bright the brightest star in

[00:39:59] terms of apparent magnitude up there in the night sky canopus is the second brightest because it's not

[00:40:05] quite as bright in apparent magnitude but then the other magnitude scale is what they call absolute

[00:40:11] magnitude this is where you even out the distances so if you say if canopus and serious were

[00:40:16] both at the same distance from us which would be the brighter one and so they've got these

[00:40:20] magnitude measurements for pretty much all the stars up there so the absolute magnitude is a more

[00:40:26] well it's a it's a measure of the intrinsic luminosity of a star so if you had all the stars

[00:40:31] lined up at the same distance then they all would appear to be certain brightnesses and but

[00:40:36] the fact is that stars are at the same distance as from us so in astronomers and people like

[00:40:40] myself talk about how bright something is in the night sky we're talking about apparent magnitude

[00:40:44] just how bright it appears to us at whatever distance that object happens to be but as i sort of

[00:40:49] explained you know um you can't judge you how bright something really is just based on what we're

[00:40:55] seeing up there because a dim star might be at a very low apparent magnitude might be very dim

[00:41:01] and apparent magnitude how we see it but it could be intrinsically very very bright and luminous

[00:41:06] and it's absolute magnitude if we put it all in that all that is standard distance that

[00:41:10] makes sense so um yeah there's just two scales so when for observational astronomy we're talking

[00:41:15] about apparent magnitude when scientists are dealing with astrophysics things they tend to

[00:41:20] work on the absolute magnitude they're even using it at all it's more more reliable equitable evened

[00:41:26] out scale where all the stars would be at the same distance from us that explains it how about

[00:41:30] the planets what's happening there the planets well the planets up uh in a pool this year well

[00:41:34] let's look at them now as the evening sky darkens we won't be able to miss seeing Jupiter

[00:41:39] i can tell you if you go out and look in the west that's the direction that the sun sets

[00:41:43] once the sun's gone down sufficiently in the sky is dark enough and it doesn't need to get too dark

[00:41:46] because Jupiter is bright you will see Jupiter it looks like a big bright prominent star above

[00:41:52] the northwest and horizon now if you have a perfect medium-sized binoculars or small telescope where

[00:41:57] you can get hold of one take a look and you should be take a look at Jupiter you should be able

[00:42:01] to see up to four tiny dots near the planet tiny bright dots perhaps two on one side and two

[00:42:07] on the other side or three on one side and one on the other side these are jupiters four

[00:42:11] largest moons the ones you've got a layer spot through his first telescope that's having

[00:42:15] yet their name the Galilean moons or the Galilean satellites and they are bright enough

[00:42:19] that you can see them through a pair of binoculars now some people have really good eyesight and

[00:42:24] some kids have actually reported this you have no super eyesight have actually been able to

[00:42:30] see these tiny pinpoints of light just with their with the naked eye you know in the

[00:42:34] good seeing conditions but it's not too much turbulent in the atmosphere and the tiny

[00:42:38] lights and moons can get through and they see the Galilean moves that's amazing yeah yeah yeah

[00:42:44] people super eyesight have reported seeing no chance I'd ever see them my eyesight isn't

[00:42:49] the best result but the great thing about them is that these moons around Jupiter so quickly

[00:42:53] without if you go out and look at them say after the sky's got dark and you won't be able to

[00:42:57] do this at the moment because Jupiter has been at a set a couple of hours after sunset

[00:43:01] but if you've got a time of the year when Jupiter is up all night then you can go out

[00:43:05] in the sky get dark have a look see what the positions of the moons are and then if you check

[00:43:09] you know hours and hours later during that same night starts going to bed and get up early in

[00:43:12] the morning when it's dark and have another look you see they've all moved because they're

[00:43:15] orbiting around the planet and sometimes they move in front of each other sometimes they disappear

[00:43:19] around behind Jupiter sometimes they just disappear into Jupiter's shadow very slow real

[00:43:24] time entertainment if you like astronomical entertainment but it is really amazing to

[00:43:28] see and it's one of the things of course that Galileo saw and figured out hey what we

[00:43:32] thought before telescopes was the unchanging heavens when everything's static everything's

[00:43:37] sane everything's perfect everything's pure and all of a sudden looks through a telescope

[00:43:40] and oh there's things pushing around other things out there a bit like the moon whizzes

[00:43:44] around the earth so that was a revelation point for Galileo wasn't it that was the yes and

[00:43:49] pretty much you know um hey you know we're not that special because it's happening out

[00:43:53] there too and if it's happening with Jupiter it's probably happening with the other ones and

[00:43:56] so on and so on and so on so yeah a lot of people credit this sort of thing as being um part of

[00:44:01] the start of a scientific revolution you know basic stuff on observation and evidence rather than just

[00:44:06] dogma and mythology and sort of thing anyhow got a little bit of talking about the planets um all

[00:44:11] the other planetary activities moment happening in the morning sky so you've got to be up early

[00:44:15] or getting home late after night shift first up we've got Mars which is rising at about 4 30 a.m

[00:44:20] at the start of April close behind it very close behind it is Saturn rising only about

[00:44:24] half an hour later and then an hour after that Venus for rise too all pretty much in the

[00:44:28] same part of the sky now it's easy to tell these three planets apart because Mars has a reddish

[00:44:33] orange color Saturn is about the same brightness as Mars at the moment but it's a white color

[00:44:38] possibly with a slightly yellowish tinge I often think it's got a slightly yellowish tinge and Venus

[00:44:43] is very different to both of them Venus is far brighter and it's bright white so you're not

[00:44:47] going to miss it so Mars comes up first then Saturn and then Venus and if you take a look in

[00:44:51] the morning go out the morning of April 11th you have to get up nice and early you'll see

[00:44:55] that Mars and Saturn would have cycled up to each other because then the moving in the sky

[00:44:59] of each night goes past they're moving a little bit and at this particular time they're sort of

[00:45:03] moving towards each other as seen from Earth and on the morning of the 11th they're only

[00:45:08] leaving about half a degree apart which is really quite close of course there are long

[00:45:11] distances apart in real-terms out there in space but just from our point of view

[00:45:14] they're a line of sight you know the only half a degree apart and that is going to look

[00:45:18] really really spectacular so fingers crossed this is in good weather on the morning of April

[00:45:22] 11th except for a long clock to get up early and have a look at that it should be really good

[00:45:26] and let's do it is the night sky for April that's Jonathan Alley from Sky and Telescope Magazine

[00:45:32] and this is Space Time

[00:45:46] and that's the show for now

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